Various approaches to making use of the after-flow energy have been proposed by the prior art as illustrated in FIGS. 1A-1E and 2A-2C.
Approach 1:
As schematically shown in FIG. 1A, for example, this approach is to employ the after-flow 2A to rotate a turbine impeller 1B which in turn rotates a rotary brush 12 for removing dust, dirt or refuse. An example of this approach is disclosed in Japanese utility model publication Kokoku No. 39-36553 published on Jul. 7, 1962.
Approach 2:
As schematically shown in FIG. 1B, for example, this approach is characterized by driving a beating vibratory means 15 by the after-flow 2A. An example of this approach is disclosed in Japanese patent publication Kokai No.3-162814 published on Jul. 6, 1990.
Approach 3:
As illustrated in FIG. 1C or 1D, for example, this approach is to direct the after-flow 2A, as jets if desired, in a direction generally parallel to the surface F being cleaned to be drawn into an opposing suction port 3 in which the flow is created by both the forcing positive pressure and the suction rather than the suction alone from the atmosphere as in the non-recirculating type cleaner. The arrangement of FIG. 1C is disclosed in the aforesaid Japanese utility model publication Kokoku No. 39-36553 and Japanese utility model publication Kokoku No. 43-22616 (published on Oct. 5, 1964). The arrangement of FIG. 1D is shown in Japanese patent publication Kokai No. 48-46157 (published on Oct. 1, 1971).
Approach 4:
As illustrated in FIG. 1E or FIG. 2B, 2C for example, this approach is to discharge the after-flow 2A in the form of a jet against the surface F being cleaned at an angle of 0.degree. to 60.degree. relative to the surface F to blow up the dust to be suctioned into an opposing suction mouth 3. The arrangements of FIG. 1E, FIG. 2B and FIG. 2C are disclosed in Japanese patent publication Kokai No. 48-101764 (published on Apr. 8, 1972), Japanese utility model publication Kokai No. 60-188553 (published on May 24, 1984) and Japanese patent publication Kokai No. 3-162814, respectively.
Approach 5:
U.S. Pat. No. 3,268,942, for example, teaches providing a recirculating flow outlet within the region of a dust collecting port, the outlet comprising a number of jet nozzles, and blowing the jet at an angle of approximately 90 deg. relative to the surface F to be cleaned, whereby the dust entrapped in grooves or between the root portions of the carpet piles may be effectively removed.
In the approaches 3 and 4, the configurations of the dust collecting port 30 (comprising an outlet 4 and a suction port 3) may take various forms:
(A) The suction port 3 is most often located within the region of the outlet 4 as illustrated in FIGS. 1C, 1D and 2A1 (Japanese patent publication Kokai No. 58-175528). In some cases, however, the dust collecting port 30 may comprise a one-sided outlet 4 and a one-sided suction port 3 as shown in FIG. 1A, 1E and 2B. PA1 (B) As illustrated in FIG. 2A2 (Japanese patent publication Kokai No. 58-2175528), a single outlet 4 may be disposed within a suction port 3. PA1 (C) In the arrangements of FIGS. 1C, 1D, 1E and 2A1, 2A2, the end surface 21 of the boundary wall between the outlet and suction regions is generally parallel to the surface F to be cleaned, and planar and smooth. PA1 (D) As illustrated in FIGS. 2C, 2A1 and 2A2, the end surface of the outer peripheral wall of the suction region may be generally parallel to the surface F, and planar and smooth.
In the aforesaid prior art cleaners except those shown in FIGS. 2B and 2C, the recirculating ratio (the amount of the flow discharged at the dust collecting port divided by the amount of the after-flow of the fan motor) appears to be 100% as far as it may be seen from the constructions shown.
In the arrangement shown in FIG. 2B a regulating valve 10 is disposed in the recirculating path 2T after the after-flow is divided into a recirculating flow 2A and an exhaust flow 2B. With this construction, it is presumed that the recirculating ratio may not exceed 50% even with the recirculating path being fully open. The regulating valve 10 may be operated either manually or by the negative pressure at the suction port.
World (Canadian Patent CA 977910) discloses employing a recirculation ratio less than 100% while discharging 5% of the air suctioned to the atmosphere in order to maintain a negative pressure inside the dust collecting port. But, the recirculation ratio is fixed. In the arrangement shown in FIG. 2C, a two-way valve 9 is disposed at the branch point. With this construction, the recirculating ratio may be varied from 100% to 0% but is set in a semi-fixed manner for the primary purpose of cooling and keeping the vicinity of the outer boundary of the dust collecting port in negative pressure. Further, Bordini (French Patent 1,542,802) illustrates the use of a short-circuit valve in the recirculating type dust collecting port for selectively connecting the suction path with the recirculating path in a short-circuit manner, the arrangement being such that the short-circuit valve may be actuated to prevent the dust from being blown up when the cleaning port comes in proximity to the surface being cleaned. It is also proposed that the short-circuit valve be actuated intermittently to cause the air jet to impact against the surface being cleaned during the cleaning operation. While the efficiency in utilization of the after-flow energy has been enhanced by the approach 5, the prior art cleaners as described hereinabove still have the following subjects to be solved:
Subject 1:
It is proposed as illustrated in FIG. 2C and as per Japanese patent application Kokai No.3-152814 by Miwa and Canadian Patent CA 977910 to World that the recirculation ratio be set at a level lower than 100% for the purpose of cooling the motor as well as preventing the dust from being scattered around a dust collecting head. On the other hand, the cleaning efficiency is higher with the recirculation ratio closer to 100%, as will be explained hereinafter. Accordingly, the operation should take place at an optimal recirculation ratio. However, a greater suction force may sometimes be needed as when the dust is relatively heavy and fine, or relatively less suction force may be needed when the surface to be cleaned is a smooth flooring, or it may be desired to strongly vacuum ticks from underneath the outer surface of `tatami` mats (Japanese straw made mats) or carpets. Further, it may be desirable to have a stronger jet in order to clean a long-piled carpet, for example. For this reason, it is desirable to control the recirculation ratio (the maximum suction at a ratio of 0% and the strongest jet at a ratio of 100%) in stepwise fashion or continuously.
FIG. 2B is an example of the conventional recirculation ratio variable system where the recirculating ratio may be varied in an ON-OFF manner or continuously. It is presumed that such a system may raise the recirculation ratio up to 50% at highest, which is insufficient to provide a satisfactory efficiency because branching comes first and later only the recirculation flow is controlled. The system shown in FIG. 2C is capable of approximately 100% to 0% regulation, but the regulation is primary for the purpose of cooling the motor fan and preventing dust scatter by the jet with the regulating valve 9 being set in a semi-fixed manner. The World patent does not disclose the specific construction of the discharge valve, the setting of which is effected in a semi-fixed manner. None of the three examples just described above permits the operator to control the recirculation ratio over a wide range and in a convenient manner during the cleaning operation.
Subject 2:
While the Bordini patent proposes providing a valve for selectively connecting the suction path with the recirculating path in a short-circuit manner, the valve being adapted to be actuated either manually or electrically to prevent the recirculating jet from scattering the dust by short-circuiting when the cleaning port comes in proximity to the surface being cleaned, the valve is operated in an ON-OFF manner, so that when actuated, it completely terminates the functions of the cleaning head (discharging and suctioning the air). That is, it is impossible to operate the cleaning head at a desired recirculating ratio. Even if the opening of the short-circuit valve were made continuously variable, the control of the opening of the short-circuit valve would change the flow to and from the cleaning head but not change the ratio of discharging to sucking (recirculation ratio) because no means are provided for branching the after-flow to be exhausted. In other words, the recirculation ratio is always 100% regardless of the opening area of the short-circuit valve the ratio. Thus, it would not be possible to vary the ratio of discharging to sucking at the cleaning head while making the full use of the flow output of the fan motor. To effect adjustment of the recirculating ratio, when required, another device must be provided separately in addition to the short-circuit valve.